The prior art is already aware of park-lock devices for use with vehicle transmissions, and these prior devices include mechanisms in the nature of latches and pawls or the like which engage the teeth of transmission gears for securing the gears in a non-rotatable position. One example of a prior art mechanism is disclosed in U.S. Pat. No. 2,875,856 which also shows a cam-type of arrangement for advancing the latch toward the gear and a spring for retracting the latch from the gear.
In these prior art devices, the latch has a lug or tooth which can be manually positioned toward the gear to be restrained, and the latch lug or tooth might or might not enter the spacing between the gear teeth to arrive at the secured position. That is, the latch lug might move directly on to the gear tooth itself, rather than into the spacing between two teeth, and, as such, the latch would not hold the gear against rotation until the latch lug would enter the spacing between the gear teeth. That prior art arrangement therefore is inefficient and not completely reliable in holding the gear against any and all rotation. Therefore, where the prior art latch does not firmly engage the gear by entering the spacing between the teeth, any movement of the gear itself can cause damage to the latch or the gear teeth when the latch does enter the spacing in response to that movement.
In contrast to the prior art, the present invention provides a park-lock mechanism for a transmission wherein the latch includes two lugs which are spaced apart at a dimension different from the spacing of the teeth of the gear which the latch secures against rotation. With this arrangement, the mechanism of this invention assures that the latch will always and immediately be set in the latching and secure position when desired, and the gear need not be rotated to a certain position to achieve the latching described. Accordingly, an improved and more reliable and secure type of mechanism is provided in this invention. Further, the mechanism of this invention is sufficiently sturdy and can be easily manipulated for positioning the latch in the secured position and in the released position, and the mechanism also includes an arrangement for retaining the parts in the secured position and also in the released position for optimum safety and reliability in the operation of the mechanism.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.